A current trend in furnace technology is that directed to the optimization of combustion efficiency and emission performance by application of tuning techniques and hardware to improve the fuel/air balance in the furnace. The intent here is to achieve as closely as possible perfectly uniform coal flow from the pulverizer to the individual burners of the furnace, i.e., to the fuel admission assemblies of the furnace, so as to thereby result in the attainment therefrom of greater combustion efficiency as well as better furnace emission performance.
Each pulverizer that is employed for purposes of supplying coal to a furnace for combustion typically is operative to supply pulverized coal to the front of each burner of a single elevation of burners. Thus, as the demand for pulverized coal increases, an additional pulverizer commonly is placed in service in order to thereby supply pulverized coal to an additional elevation of burners that are suitably provided for this purpose within that the same furnace. Similarly, as demand for pulverized coal decreases, an elevation of burners, as well as the pulverizer that is being employed to supply pulverized coal thereto, are commonly each removed from service. Typically, single furnaces, such as, by way of exemplification and not limitation tangentially fired pulverized coal furnaces in which pulverized coal that is entrained in air is designed to be fired, are designed for this purpose so as to be rectangular in cross-section and such as to have four burners per elevation. Each such burner typically is located at a respective one of the corners of the furnace. Continuing, pipes that are designed to be operative to deliver pulverized coal therethrough are suitably positioned so as to terminate at the front of each burner of the same elevation of burners. Such coal delivery pipes are designed to originate at a single one of the pulverizers. Commonly, no two coal delivery pipes that originate from the same pulverizer are found either to be of the same length or to traverse the same path.
To this end, because such coal delivery pipes are of different lengths and traverse different paths, no two coal delivery pipes embody the same pressure drop from end to end thereof. On the other hand, if a uniform pressure drop were to exist in each coal delivery pipe, this would result in a near uniform coal flow in each one of the coal delivery pipes. As such, in order thus to compensate for the differing pressure drops in the coal delivery pipes, it is known that riffles, orifices, and/or splitters, each of which being adjustable have been utilized in the prior art in association with such coal delivery pipes for purposes of effecting therewith the redirection of coal flow and/or the adjustment of pressure drops in order to thereby achieve as a result of the use thereof a balancing of coal flow among each of the coal delivery pipes. This form of methodology is often referred to in the art as coal balancing.
In order to render it possible to properly adjust such riffles, orifices, and/or splitters, it is necessary that the total coal flow in each of the coal delivery pipes be accurately measured. To this end, there are many two phase coal flow measurement devices, which are suitable for use for this purpose that are known to be commercially available. Continuing, such commercially available two phase coal flow measurement devices are known to employ a variety of different principles of operations. By way of exemplification and not limitation in this regard, some such two phase coal flow measurement devices are known to be operative to physically collect samples of pulverized coal from across each one of the coal delivery pipes and, by virtue of the subsequent weighing of such pulverized coal samples, can produce therefrom a relative indication of the pulverized coal flow through the coal delivery pipes in question. In addition there are also known to exist a variety of either two phase devices, which are operative to provide a real time indication of the pulverized coal flow through coal delivery pipes based on the use of optical, acoustic vibration, electrostatic, or microwave forms of methodologies. In this regard, such optical devices commonly use light scattering methods in order to thereby determine therefrom particle size as well as the amount of pulverized coal loading. On the other hand, acoustic vibration devices are designed to be operative to relate variations in the resonant frequency of the pulverized coal stream in the coal delivery pipes in order to thereby effect therefrom a measurement of the pulverized coal flow rate. Continuing, electrostatic sensors are designed to be operative to measure the electric charge on the pulverized coal particles in the coal delivery pipes in order to thereby produce therefrom an indication of the relative mass flow and velocity thereof. Lastly, microwave based devices are designed to be operative to employ microwave transmitters and receivers that are located in situ in order to thereby produce therefrom an indication of pulverized coal flow density as well as an inferred pulverized coal flow rate.
The two phase coal flow measurement devices that are commonly available are not only known to be expensive, but are also known to lack measurement accuracy when employed in those situations wherein considerable coal roping occurs. Continuing, it has been found that coal roping commonly creates measurement errors due to the fact that variations exist in the two-phase fluid flow density. Coal roping is generally defined as being a concentration of pulverized coal in a relatively small area of a coal delivery pipe. To this end, the pulverized coal that is entrained in the coal/air mixture, which exits from a pulverizer, is dragged by the flowing medium, causing such pulverized coal to lag insofar as changes in the flow pattern thereof is concerned, due to the configuration of the coal delivery pipe. That is, a coal rope is created as a result of the centrifugal flow patterns that are established by virtue of the elbows and pipe bends that are present in the coal delivery pipe. Continuing with the description thereof, the exact position of such a coal rope within the coal delivery pipe, as well as the size of such coal rope, will vary with time and thus the coal rope's existence cannot be accurately predicted insofar as the location thereof within the coal delivery pipe is concerned, nor can the size of such a coal rope be accurately determined. As such, the existence of such coal roping functions to prevent coal flow from being accurately measured in a coal delivery pipe. In addition, such coal roping is also operative to cause the coal balancing between various coal delivery pipes to be inexact.
Accordingly, a need has been found to exist for a new and improved apparatus (a) that is capable of being employed to measure the coal flow in a coal delivery pipe notwithstanding the presence therein of coal roping, (b) that is capable of effecting therewith a balancing of the coal flow in a coal delivery pipe notwithstanding the presence therein of coal roping, and (c) that is operative for purposes of detecting therewith the presence of a coal rope within a coal delivery pipe.